Tensioner for continuous web rewind roll

Abstract

A tensioner for controlling tension in a continuous web being wound onto a rewind roller after the web is processed, for example after printing on labels carried on the web. The tensioner receives the web from a processor and has a slack sensor between the processor and the input of the tensioner. The slack sensor indicates when the slack is a selected minimum, and the web is clamped by the tensioner. After a selected time, which is before the slack sensor indicates a maximum slack is present, the motor driving the rewind roller is stopped and the web is unclamped. After unclamping the web, the rewind roll is again driven at a speed to take up more of the web than that which is driven by the processor, to wrap the web around the core until the slack sensor indicates the slack in the web is at a minimum.

1 . A tension control device for a continuous web to be wound onto a roll having a motor for rotatably driving the roll for winding the web, the tension control device comprising:
 a web restraint operable to prevent movement of the web;   a control to initiate the motor to drive the roll to tighten portions of the web on the roll when the web restraint is operated to prevent movement of the web; and   a release mechanism to release the web restraint to permit movement of the web when the roll is rotatably driven by the motor.   
     
     
         2 . The tension control device of  claim 1  including a processor to drive the web to an infeed of the tension control device, a web slack sensor sensing slack in the web being driven to the infeed, the web restraint being operated for preventing movement of the web when the web slack sensor indicates a selected slack in the web, and a second sensor to provide a signal starting the motor for driving the roll when the web is prevented from movement. 
     
     
         3 . The tension control device of  claim 2  wherein the web slack sensor provides a second signal indicating that the slack in the web is a selected maximum, the motor being timer controlled to stop driving the roll before the web slack sensor provides the second signal. 
     
     
         4 . The tension control device of  claim 2 , wherein the processor drives the web to the infeed at a first lineal speed, and the motor drives the roll at a speed to provide a lineal speed of the web greater than the first lineal speed when the web restraint is released. 
     
     
         5 . The tension control device of  claim 2 , wherein the web slack sensor comprises a rotatable sensing roll mounted to move relative to a path of movement of the web between the processor and the infeed, said sensing roll being moved by the web between a first position indicating at least a reduced slack in the web, and a second position indicating a maximum desired slack in the web. 
     
     
         6 . The tension control device of  claim 5 , wherein said sensing roll is mounted on an arm, said arm being pivoted relative to the tension control device to permit the sensing roll to move in an arc as the sensing roll moves between the first and second positions. 
     
     
         7 . The tension control device of  claim 1 , wherein the web restraint comprises clamp pads that are spaced apart, with the web passing between the clamp pads, and wherein the release mechanism moves one of the clamp pads away from the other clamp pad. 
     
     
         8 . A tension control device of  claim 1  further comprising a timer to control the motor to rotate the roll for a set period of time after the web restraint has been operated to prevent movement of the web. 
     
     
         9 . The tension control device of  claim 1 , and further comprising a controller receiving a signal indicating that a web length at an infeed of the tension control device is slack and thereafter operating the release mechanism to release the web restraint and to start the motor to drive the roll. 
     
     
         10 . The tension control device of  claim 9  including a web slack sensor providing a signal to the controller when the slack in the web length at the infeed of the tension control device is at a selected minimum, to operate the clamp to prevent movement of the web, and to initiate the motor to drive the roll to tighten portions of the web on the roll. 
     
     
         11 . The tension control device of  claim 9  wherein said motor drives the roll, after the web restraint is released by the release mechanism such that the web moves at a lineal speed which reduces slack in the web length at the infeed of the tension control device. 
     
     
         12 . The tension control device of  claim 1 , wherein said web restraint comprises a clamp and further comprising guides for guiding the web through the clamp and to the roll. 
     
     
         13 . A tension control system for regulating the tension in a continuous web as the web is wound onto a rewind roll from a printer driving the web, the printer having a web feed driving the web through the printer, the tension control system including a tensioner assembly between the printer and the rewind roll associated with the web, said tensioner assembly having a slack sensor for sensing slack in the web between the printer and the tensioner assembly, and a web restraint to prevent movement of the web around the rewind roll, a motor to drive the rewind roll to rewind a web thereon when the web restraint is positioned to permit movement of the web, and to tighten the web onto the roll at selected intervals when the web is prevented from movement around the rewind roll. 
     
     
         14 . The tension control system of  claim 13 , and a slack sensor operable to sense a slack in the web between the printer and the tensioner assembly, sensors to sense a position of the slack sensor indicating the amount of slack in the web between the printer and tensioner assembly, and a controller to periodically cause the motor to drive the rewind roll to rewind the web onto the rewind roll when the web is permitted to move by the web restraint, and to cause the motor to rotate the rewind roll to tighten loose lengths of the web on the rewind roll when the web is prevented from movement from the printer to the rewind roll. 
     
     
         15 . The tension control system of  claim 13  wherein said web restraint comprises a clamp and further comprising a clamp control to release the clamp and permit the web to be rewound on the rewind roll when the slack in the web between the printer and the tensioner assembly is indicated as being a selected amount, and to operate the clamp to clamp the web when the slack sensor indicates when the slack of the web between the printer and the tensioner assembly is at a selected minimum amount. 
     
     
         16 . The tension control system of  claim 13 , wherein said web restraint comprises a clamp, a spring to spring load the clamp to a clamping position to restrain the web, and a release mechanism to release the clamp against the spring load in response to a signal from the slack sensor. 
     
     
         17 . A method of controlling wrapping of a an elongated web onto a rewind roll, comprising driving the web longitudinally lineally from a processor, providing a driven rewind roller to take up the elongated web from the processor, providing a web restraint to selectively restrain the web from longitudinal lineal movement, periodically restraining the web and driving the rewind roller while the web is restrained to tighten lengths of the web previously wound on the rewind roller. 
     
     
         18 . The method of  claim 17 , including sensing slack of the web between the processor and the web restraint to provide signals to selectively restrain and release the web for longitudinal lineal movement at selected intervals. 
     
     
         19 . The method of  claim 18  including driving the rewind roller at a speed such that the web has a lineal speed when the web is released that is greater than a lineal speed of the web as driven by the processor. 
     
     
         20 . The method of  claim 17  including providing a clamp for forming the web restraint, sensing slack of the web between the processor and the clamp and clamping the web with the clamp to restrain longitudinal lineal movement of the web when slack of the web between the processor and the clamp is a selected minimum. 
     
     
         21 . The method of  claim 20  including sensing when slack of the web between the processor and the clamp is at a selected maximum after the web is clamped by the clamp, stopping the drive to the rewind roller prior to the time slack of the web reaches its selected maximum, and releasing the clamp to permit the web to move when the selected maximum slack is sensed. 
     
     
         22 . The method of  claim 21  and further comprising driving the rewind roller after the clamp is released until slack of the web between the processor and the clamp is sensed to be at the selected minimum.